1. Field of the Invention
The present invention relates to a process for producing a delivery belt for delivering precision parts with high positional accuracy, a film in a shape of a circle, tube, sleeve, ring, or belt for tight packing of articles, or a tubular article. The present invention is applied mainly to functional parts of image-forming apparatus.
2. Related Background Art
Conventionally, tubular articles having a metal layer as a part are produced typically by the methods below:
(1) Extrusion of a plastic material in a tube form by hot melt extrusion such as inflation around a metallic tube, and succeeding solidification by cooling, PA0 (2) Casting of a solution of a resin or a resin precursor onto an external or internal surface of a metallic tube in a prescribed amount, and succeeding removal of the solvent (heat treatment if necessary), and PA0 (3) A method disclosed by the inventors of the present invention (Japanese Patent Application Laid-Open No. 8-187773) in which a thermoplastic sheet film is wound on a cylindrical member with the wind-ending portion of the film laid on the wind-starting portion of the same film, a tubular member is fitted outside the wound film, and the entire is heated to join the overlapped portion of the film to form the sheet film into a tube, at least one of the thermoplastic sheet film having a layer containing metal powder dispersed therein.
In the hot melt forming method of the above item (1), when the tubular article produced by inflation is used as a film 20 of a fixation device of an image-forming apparatus as shown in FIGS. 10A and 10B, the tubular article is deformed irreversibly during the a sheet-drawing operation disadvantageously. The deformed tubular article will not recover the original shape since the tubular article has a metal layer as a part.
The casting method of the above item (2) involves the problems of difficulty in controlling the solution concentration, and in adjusting the drying atmosphere; the cost in solvent treatment in the drying step; and so forth in order to obtain a uniform thickness of the film.
In the method of the above item (3), a sheet film is wound with the one winding end is laid on the other winding end, a tubular member is fitted outside it, the level difference at the overlapping portion is flattened by decease of the gap distance between the cylindrical member and the tubular member by heat expansion to obtain a tubular film. In this method, the characteristic metal properties (e.g., thermal conductivity, and electroconductivity) are partly lost because metals should be contained in a thermoplastic resin in a powdery form.